Features: Brand new and high quality Best performances sound signal Amplifiers with Volumes control adopts Sound signal amplification circuit architecture, and the output level signal gain is +20dB. USB 5V power, suitable for outdoor mobile power. Input and output adopt 3.5mm, which is suitable for more devices. Easy installation, you can enjoy a different Sound experience. Enhances the input signal and more delicate. Specifications: Material:Metal Input impedance: 100KOhm Output gain: +20dB Frequency response: 20Hz-20KHz Signal to noise ratio: >107dB Intermodulation distortion: <0.01% Input port: stereo 3.5mm Output port: stereo 3.5mm Power supply: USB 5V Size: 108x75x38mm/4.25x2.95x1.5inch Package Includes: 1Pc Sound Amplifiers note: 1.Please allow 1-2cm errors due to manual measurement, make sure that you not mind before order. 2.Due to the differences between different monitors, the picture may not reflect the actual of the item.